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Old 11th Mar 2008, 12:48 pm   #1
dave.mycock
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Default Vidor CN426 HENLEY

Hello All
I am a beginner and trying to get this set working. At the moment it is totally dead, no crackles from wavechange switch. I am puzzled as to why the HT is very high, ie 116v on the anode of DL94 all other anode volts are also very high. I have tried the valves in another set and they work ok. I get a crackle from the speaker when i flash a battery across the o/put transformer primary.
any help would be much appreciated.
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Old 11th Mar 2008, 1:42 pm   #2
geofy
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Post Re: Vidor CN426 HENLEY

Hi Dave
The HT for this set should only be 90Volts from a battery, if it is from a mains supply this is set to high, are all the valve heaters alight, though if the HT is to high the heater voltage might be as well.

The various inter stage capacitors/resistors should be checked, one may be open circuit, ideally a I.F. signal should be injected to see if this gets through to the speaker, it could be the high HT is because the set isn't oscillating. A screwdriver tapped on the volume control tags should produce a crackle in the speaker to show the audio stage is working. Or a signal taken from here to another audio amp to show the R.F. I.F. is working if the fault is in the audio stage.

Geof
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Old 11th Mar 2008, 1:52 pm   #3
yestertech
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Default Re: Vidor CN426 HENLEY

It sounds as though there is no supply to the valve heaters. These appear to be series fed from the HT line via ballast resistors. Check these are OK ( R19 /R20 ) If so, suspect a faulty contact in one of the valveholders interupting the heater chain... this can be tested by measuring ohms, with power removed, from the "low" side of R19 to chassis. If missing here, switch to "BATT" and do the same test from the LT + battery connection - there may be problems in the mains/Battery switching.
Andy
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Old 11th Mar 2008, 2:18 pm   #4
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Default Re: Vidor CN426 HENLEY

If you can see a glow with these valves, you're seriously overrunning them. They should also come 'straight on'.

Does this set have series or parallel valve heaters? (I'm not at home, so not got a circuit handy.) Usually parallel, but sometimes series.

Apart from the lower voltages and heaters being a bit different, they are like any other valve set. Get your avo and check valve heaters first. Then check to see whether each valve is receiving volts.

Is the speaker and O/P transformer OK. Unlikely but possible.

Cheers,

Steve P.
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Old 11th Mar 2008, 2:39 pm   #5
Robert Darwent
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Default Re: Vidor CN426 HENLEY

Hello Dave,

Quote:
Originally Posted by geofy View Post
...are all the valve heaters alight...
This set uses the following valves; DK92, DF91, DAF91, DL94 which are all battery types so there should be no visible glow to be seen from their heaters. If there is then switch off immediately! Steve's statement below is spot on;

Quote:
Originally Posted by Steve_P View Post
If you can see a glow with these valves, you're seriously overrunning them. They should also come 'straight on'.
I have to agree with Andy's assessment regarding the LT supply not reaching one or more of the valves. I've had this problem before in other Vidor sets which use McMurdo socket bases. The forked pin clinchers tend to fracture in the socket and so lose contact with the valve pins.

Regards
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Last edited by Robert Darwent; 11th Mar 2008 at 2:47 pm.
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Old 11th Mar 2008, 4:33 pm   #6
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Default Re: Vidor CN426 HENLEY

I have several similar Vidor sets and when the heaters are running at the correct voltage (1.4v) you can just and just see a dull red glowing cord of light in a pitch dark room in the centre of each valve.

Cheers
Lee
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Old 11th Mar 2008, 4:42 pm   #7
geofy
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Post Re: Vidor CN426 HENLEY

It is difficult to determine if the valve heaters are working, a milliamp meter in the LT supply might be a better way to see if heater current is being drawn.

Geof

Quote:
Originally Posted by Hunts smoothing bomb View Post
I have several similar Vidor sets and when the heaters are running at the correct voltage (1.4v) you can just and just see a dull red glowing cord of light in a pitch dark room in the centre of each valve.

Cheers
Lee
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Old 11th Mar 2008, 4:48 pm   #8
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Default Re: Vidor CN426 HENLEY

Quote:
Originally Posted by geofy View Post
It is difficult to determine if the valve heaters are working, a milliamp meter in the LT supply might be a better way to see if heater current is being drawn.

Geof
spot on Geof, should see about 50mA if things are good.

Cheers
Lee
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Old 11th Mar 2008, 7:20 pm   #9
Robert Darwent
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Default Re: Vidor CN426 HENLEY

Quote:
Originally Posted by geofy View Post
...a milliamp meter in the LT supply might be a better way to see if heater current is being drawn.
I believe the expected total current consumption from the LT supply should be around 250mA for the four valve types specified in this set. A reading significantly less than this value would indicate one or more of the valves not drawing from the LT supply. Likely due to either o/c filament(s) or poor contact in the socket base(s).

Regards
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Last edited by Robert Darwent; 11th Mar 2008 at 7:27 pm.
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Old 11th Mar 2008, 8:31 pm   #10
geofy
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Post Re: Vidor CN426 HENLEY

Quote:
Originally Posted by rrdmpb View Post
I believe the expected total current consumption from the LT supply should be around 250mA for the four valve types specified in this set. A reading significantly less than this value would indicate one or more of the valves not drawing from the LT supply. Likely due to either o/c filament(s) or poor contact in the socket base(s).

Regards
The DL94 being center tapped heater, is that 50mA per section or total for that valve expect it is 50mA per section making the 250mA total heater current.

Geof
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Old 11th Mar 2008, 10:44 pm   #11
Robert Darwent
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Default Re: Vidor CN426 HENLEY

Quote:
Originally Posted by geofy View Post
The DL94 being center tapped heater, is that 50mA per section or total for that valve expect it is 50mA per section making the 250mA total heater current.
That's correct Geof. Each section of the DL94 heater is rated at 50mA. Looking at the schematic for the 'Henley' it shows both sections connected in parallel so the valve will be drawing 100mA. As you're probably aware, in some set's provision is made for the user to change between one or both filament sections of the output valve(s) with an 'economy' switch in order to prolong battery life. Not used in this set though apparently.

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Old 12th Mar 2008, 2:46 pm   #12
dave.mycock
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Default Re: Vidor CN426 HENLEY

Many thanks to all.
With your help I've traced a broken socket pin 1 in valve 3.
When I poke it to make a connection the set now hums, no stations as yet but at least it's not totaly deaf.
Will now change valve holder (bit of a fiddle!).
Will let you know how I get on.
Regards Dave
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Old 12th Mar 2008, 4:56 pm   #13
Tim
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Default Re: Vidor CN426 HENLEY

Hi Dave
With some types of socket it is possible to change individual pins/contacts.
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Old 12th Mar 2008, 7:35 pm   #14
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Default Re: Vidor CN426 HENLEY

The heaters in the Henley are series connected for both mains and battery operation. Any open circuit heater will therefore stop all heaters working. With no heaters there is no anode current and with no anode current the HT voltage could easily rise to 115 volts. The easiest way to check the valve heaters is with an ohmeter (Digital or analogue). If all are OK then then clean the valve heater pins. If this does not solve the problem look at the valve bases (check for heater continuity on the valve base. Check the heater supply from the mains transformer and check the 2 parts of the metal rectifier (ohmeter should read high one way and low with the connections reversed). The other thing to check is the switch. From the rectifier there are two resistors in series (1.4K and 700, check for open circuit) and these then connect to the DL94 heater via the rotary switch (battery, off, mains). Check for switch closure (ohmeter) or temporarily short out the switch. Trader sheet 1155 has all the info you will need (on CD 1).
Hope this is useful.

John
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Old 13th Mar 2008, 12:06 pm   #15
Robert Darwent
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Default Re: Vidor CN426 HENLEY

Quote:
Originally Posted by Mullard View Post
The heaters in the Henley are series connected for both mains and battery operation. Any open circuit heater will therefore stop all heaters working.
Whoops! You are correct John. Don't know which Vidor pdf I clicked on the other day but it wasn't for the 'Henley'!

The valves are series connected in this set with the two filament halves of the DL94 also in series, not parallel as I stated previously. So a poor heater pin connection in any of the valves will obviously break the heater chain and stop all the valves from working.

And it appears that is the case since Dave has now reported finding a broken pin clincher at pin 1 in one the sockets.

Regards
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Old 3rd Apr 2008, 11:01 am   #16
dave.mycock
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Default Re: Vidor CN426 HENLEY

Hi all
Many thanks to all who helped.
I have had to replace 10 of those little tuning fork shaped valve holder sockets, they where either broken or making poor contact, Iv'e gone right off McMurdo holders.
The set now works fine, another bit of radio history repaired.
Thanks again Dave
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Old 3rd Apr 2008, 4:27 pm   #17
yestertech
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Default Re: Vidor CN426 HENLEY

Well done for your perseverance Dave !
Memories of multiple holder swap outs on my MB60
When you get to the third faulty holder, you do tend to question your sanity !
Luckily faith is restored on hearing the first sounds emanate from the set ,usually in several decades.

Andy
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Old 3rd Apr 2008, 4:58 pm   #18
Robert Darwent
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Default Re: Vidor CN426 HENLEY

Quote:
Originally Posted by dave.mycock View Post
I have had to replace 10 of those little tuning fork shaped valve holder sockets, they where either broken or making poor contact, Iv'e gone right off McMurdo holders.
Quote:
Originally Posted by setsappeal View Post
Luckily faith is restored on hearing the first sounds emanate from the set ,usually in several decades.
Hello Dave,

Yes well done for sticking with it. And I thought I'd been unlucky to have to replace 5 broken fork pins in my Vidor Vanguard!

But like Andy has commented its all worth that effort to here a set working again like it should.

Regards
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